Imaging devices, methods of forming same, and methods of forming semiconductor device structures

ABSTRACT

An imaging device comprising a first region and a second region. Imaging features in the first region and assist features in the second region are substantially the same size as one another and are formed substantially on pitch. Methods of forming an imaging device and methods of forming a semiconductor device structure are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/986,836, now U.S. Pat. No. 8,440,371, issued May 14, 2013, thedisclosure of which is hereby incorporated herein in its entirety bythis reference.

TECHNICAL FIELD

Embodiments of the present disclosure relate to photolithographicprocesses and, more specifically, to improving photolithographicprocesses utilizing imaging devices having array features and assistfeatures of substantially the same size and formed substantially onpitch, methods of forming such imaging devices, and methods of formingsemiconductor device structures utilizing the imaging devices.

BACKGROUND

Reticles are often used to form patterns on integrated circuit wafers.As pattern dimensions decrease, critical dimension (CD) proximity effectbecomes a significant problem and methods to correct for the proximityeffect problems are used. Optical proximity correction (OPC) is a methodof eliminating deviations in the critical dimensions of a device due toa proximity effect. The proximity effect occurs when radiation, such aslight, is projected onto a reticle having a pattern thereon. Due todiffraction of the radiation by the reticle, which may also becharacterized as scattering, the radiation diverges and spreads. Thediffracted light creates multiple diffraction orders, not all of whichare captured by a lens of an optics system. The lens captures a portionof the light, which is directed to a surface of a semiconductorsubstrate. In addition, a portion of the radiation passing through aphotoresist material on the semiconductor substrate is reflected by thesurface of the underlying semiconductor substrate, causing lightinterference and leading to overexposure of the photoresist material inpart of the pattern, which causes defects, such as optical distortions(i.e., rounding), in the photoresist material. While OPC methods areused to correct for these defects, conventional OPC methods arecomplicated because computer software must be utilized to calculatewhere the optical distortions are likely to occur. Conventional OPCmethods also rely on empirical data. However, empirical-based solutionsto OPC require protracted time, and many mask iterations, in order to besuccessfully developed.

Assist features, such as serif features, hammerhead features, andoutrigger features, are also used in conventional OPC methods. Theassist features are formed at sub-resolution scale relative to thepatterns on the reticle, which correspond to the features to be formedon the semiconductor substrate. While conventional assist features arenot imaged (e.g., printed) on the semiconductor substrate, these assistfeatures cause additional diffraction and scattering of the radiationdue to the production of diffractive signals that may be at a high angleof attack and go through edges of a lens in the optics system. Theconventional assist features are sensitive to aberrations since theyenable imaging of the features on the semiconductor substrate but donot, themselves, participate in the imaging. Use of such assist featuresin conventional OPC methods causes problems in CD uniformity (CDU) andCD bias control in both production and simulation/modeling.

It would be desirable to achieve a photolithography process having fewermask manufacturing problems, imaging quality problems, CD, and CDUproblems.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1-3 are top down views of imaging devices according to embodimentsof the present disclosure;

FIG. 4 is a side view of a pattern formed on a semiconductor devicestructure according to an embodiment of the present disclosure;

FIG. 5 is a simulated, dose-to-clear curve (relative intensity ofradiation as a function of photoresist thickness) generated using theimaging device of FIG. 3;

FIG. 6 is a top down view of an imaging device of the prior art;

FIG. 7 is a simulated dose-to-clear curve (relative intensity ofradiation as a function of photoresist thickness) generated using theimaging device of FIG. 6;

FIG. 8 is a side view of a pattern formed on a semiconductor devicestructure according to an embodiment of the present disclosure;

FIG. 9 is a simulated dose-to-clear curve (relative intensity ofradiation as a function of photoresist thickness) generated using theimaging device of FIG. 1;

FIG. 10 is a top down view of an imaging device of the prior art;

FIG. 11 is a simulated dose-to-clear curve (relative intensity ofradiation as a function of photoresist thickness) generated using theimaging device of FIG. 10;

FIG. 12 is a simulated dose-to-clear curve (relative intensity ofradiation as a function of photoresist thickness) generated using theimaging device of FIGS. 2A and 2B; and

FIGS. 13 and 14 are top down views of imaging devices according toembodiments of the present disclosure.

DETAILED DESCRIPTION

Imaging devices (e.g., photomasks, such as reticles) for formingsemiconductor device structures are disclosed, as are methods of formingthe imaging devices and methods of forming semiconductor devicestructures. The imaging device may include at least one array patternregion and at least one attenuation region on a substrate. The at leastone array pattern region may include imaging features that correspond toarray features ultimately to be formed on the semiconductor devicestructure. In one embodiment, the at least one attenuation region mayinclude assist features that are configured to at least significantlyattenuate (e.g., block) radiation such that corresponding features arenot formed on the semiconductor device structure. In another embodiment,the at least one attenuation region may include assist features and atleast one pixilated structure that are configured to at leastsignificantly attenuate (e.g., block) radiation such that correspondingfeatures are not formed on the semiconductor device structure. The arrayfeatures on the semiconductor device structure are often desirablysubstantially the same size as one another and formed substantially onpitch. Therefore, the imaging features in the array pattern regions arealso substantially the same size as one another and substantially formedon pitch. The assist features in the attenuation region aresubstantially the same feature size as one another and substantially thesame feature size and pitch as the imaging features. The periodicity ofthe imaging features and the assist features may provide good CD and CDUto the array features ultimately formed on the semiconductor devicestructures.

The imaging devices of the present disclosure enable the transmittanceof different amounts of radiation through different regions of theimaging device. Since the periodicity of the assist features may bemaintained at a constant (e.g., uniform) pitch across the attenuationregion, the array pattern regions may be easier to image. Therefore, anoptics system in a photolithography process utilizing the imagingdevices may view the imaging features (in the array pattern regions) andthe assist features (in the attenuation region) as a gray scale and as auniform field. By forming the imaging features and the assist featuresat substantially the same size and pitch, diffraction consistency acrossthe array and periphery is improved. In addition, the image quality ofthe imaging features and, thus, the image quality of the array featuresmay be maintained. By utilizing the imaging devices and methods of thepresent disclosure, imaging may be fundamentally improved, such asimaging employed in the fabrication of flash memory.

The following description provides specific details, such as materialtypes, material thicknesses, and patterns in the imaging devices inorder to provide a thorough description of embodiments of the presentdisclosure. However, a person of ordinary skill in the art willunderstand that the embodiments of the present disclosure may bepracticed without employing these specific details. Indeed, theembodiments of the present disclosure may be practiced in conjunctionwith conventional fabrication techniques employed in the industry. Inaddition, the description provided below does not form a completeprocess flow for manufacturing a semiconductor device. The semiconductordevice structures described below do not form a complete semiconductordevice. Only those process acts and structures necessary to understandthe embodiments of the present disclosure are described in detail below.Additional acts to form the complete semiconductor device from thesemiconductor device structures may be performed by conventionalfabrication techniques.

The materials described herein may be formed by any suitable techniqueincluding, but not limited to, spin coating, blanket coating, chemicalvapor deposition (CVD), atomic layer deposition (ALD), plasma enhancedALD, or physical vapor deposition (PVD), unless otherwise specified.Alternatively, the materials may be grown in situ. Depending on thespecific material to be formed, the technique for depositing or growingthe material may be selected by a person of ordinary skill in the art.While the materials described and illustrated herein may be formed aslayers, the materials are not limited thereto and may be formed in otherthree-dimensional configurations.

The illustrations presented herein are not meant to be actual views ofany particular semiconductor device structure, but are merely idealizedrepresentations that are employed to describe the present disclosure.The figures are not necessarily drawn to scale. Additionally, elementscommon between figures may retain the same numerical designation.

A desired pattern of array features to be formed on the semiconductordevice structure may be achieved by enabling the transmission ofdifferent amounts, which may also be characterized as magnitudes (i.e.,intensities), of the radiation to pass through the imaging device. Byway of example, the array pattern regions of the imaging device mayenable the transmission of a higher percentage of the radiationtherethrough to form the array features on the semiconductor devicestructure, while the attenuation regions may enable the transmission ofa lower percentage of the radiation therethrough. Therefore, featurescorresponding to the assist features located in the attenuation regionsmay not be formed on the semiconductor device structure. The assistfeatures may be formed from a radiation attenuating material such thatan attenuated amount of radiation passes through the attenuation regionsof the imaging device. The radiation attenuating material may beselected to provide a desired degree and phase of attenuation of theradiation. The array features to be formed on the semiconductor devicestructure may be dense features, isolated features, or combinationsthereof. As used herein, the terms “dense feature” and “isolatedfeature” refer to the relative proximity of individual features to oneanother on the semiconductor device structure. The dense features may bein close proximity to one another on the semiconductor device structurewhile the isolated features may be spaced farther apart from oneanother. The semiconductor device structure may also include a region inwhich the dense features transition into the isolated features. Forconvenience, such a transition region is referred to herein as aso-called “iso-dense region.” The iso-dense region is a portion of thesemiconductor device structure that transitions from array features toassist features. The array features may be substantially one-dimensionalfeatures in the major plane of the semiconductor device structure, suchas conductive lines, such as access lines (i.e., wordlines), ortwo-dimensional features, such as contacts.

The method of the present disclosure may utilize the imaging devicehaving the at least one array pattern region and the at least oneattenuation region to form the desired pattern on the semiconductordevice structure. As shown in FIG. 1, the imaging device 2 may include asubstrate 4 having assist features 6 formed thereon that are configuredto at least partially attenuate radiation that passes therethrough.Other imaging devices 2′, 2″, 2″′, 2″″ are shown in FIGS. 2A, 2B, 3, and13. The assist features 6 may, for example, be configured tosubstantially block radiation that passes through the imaging device 2′,2″, 2″′, 2″″. The assist features 6 may be formed from an opticallyopaque material that attenuates the radiation. As used herein, the term“optically opaque,” or grammatical equivalents thereof, means andincludes a material that is configured to intercept (e.g., absorb) theradiation to which the imaging device 2, 2′, 2″, 2′″, 2″″ is exposed.The imaging device 2, 2′, 2″, 2″′, 2″″ may also include imaging features8, which are formed from an optically opaque material or a partiallytransmissive material. As used herein, the term “partially transmissivematerial,” or grammatical equivalents thereof, means and includes amaterial through which a portion of the radiation of a selectedwavelength or wavelength range passes when the imaging device 2, 2′, 2″,2′″, 2″″ is exposed to such radiation, for example, during aphotolithographic process. By way of example, the partially transmissivematerial may include, but is not limited to, molybdenum silicon (MoSi),molybdenum-doped silicon oxide (MoSi_(x)O_(y)), molybdenum-doped siliconoxynitride (MoSi_(x)O_(y)N_(z)), molybdenum-doped silicon nitride,molybdenum silicide, chromium oxide (CrO), tantalum silicon oxynitride(TaSiON), or combinations thereof, wherein “x,” “y” and “z” are numbersgreater than zero. The partially transmissive material may enableapproximately 6%, approximately 20%, approximately 30%, or approximately40% of the radiation to pass therethrough, depending on the materialselected. Partially transmissive materials that enable 6% or 20% of theradiation to pass therethrough are known in the art. The imagingfeatures 8 may be 180° out of phase with open areas on the imagingdevice 2 and the assist features 6. As previously described, the assistfeatures 6 may form attenuation region 10 and the imaging features 8 mayform array pattern region 12. The substrate 4 may be formed from amaterial that is optically transparent to a wavelength or range ofwavelengths of radiation to which the imaging device 2, 2′, 2″, 2″′, 2″″is to be exposed. As used herein, the term “optically transparent,” orgrammatical equivalents thereof, means and includes a material throughwhich substantially all radiation of a selected wavelength or wavelengthrange passes when the imaging device 2, 2′, 2″, 2″′, 2″″ is exposed tosuch radiation, for example, during a photolithographic process. By wayof example, the optically transparent material may be quartz. In FIGS.1-3 and 13, the regions of the imaging device 2, 2′, 2″, 2′″, 2″″through which radiation passes (those formed of the opticallytransparent material) are indicated in white, the regions of the imagingdevice 2, 2′, 2″, 2″′, 2″ through which radiation is substantiallyblocked (those formed of the optically opaque material) are indicated inblack, and the regions of the imaging device 2, 2′, 2″, 2″′, 2″″ throughwhich radiation is at least partially blocked are indicated in gray (theassist features 6, a pixelated structure 14, or imaging features 8).

In some embodiments of the imaging device 2, 2′, 2″, 2″′, 2″″, theassist features 6 at least partially attenuate radiation by forming theassist features 6 from a material formulated, at the thickness of theassist features 6, to partially attenuate the radiation. The radiationattenuating material may be selected based on its extinction coefficient(k) to achieve a desired percentage of attenuation (partialtransmissivity) of the radiation. The radiation attenuating material mayblock a known percentage of radiation of a particular wavelength orwavelength range from passing through the attenuation regions 10 whilepermitting a remainder of the radiation to pass therethrough. Theradiation attenuating material may be MoSi, MoSi_(x)O_(y),MoSi_(x)O_(y)N_(z), molybdenum-doped silicon nitride, molybdenumsilicide, CrO, TaSiON, or combinations thereof, wherein “x,” “y” and “z”are numbers greater than zero. In one embodiment, the radiationattenuating material is MoSi. By way of example, the radiationattenuating material may be a MoSi that in configured to block 6% of theradiation or to block 20% of the radiation. The radiation attenuatingmaterial may be formed on the substrate 4 by conventional techniques,such as by chemical vapor deposition (CVD) or physical vapor deposition(PVD). The assist features 6 may be formed from the radiationattenuating material by patterning the radiation attenuating material,such as by using conventional photolithography techniques, which are notdescribed in detail herein. The thickness of the radiation attenuatingmaterial for effective attenuation of radiation may depend on thewavelength or range of wavelengths of radiation to which the imagingdevice 2, 2′, 2″, 2′″, 2″″ are to be exposed and on the desired degreeof transmissivity of radiation through the imaging device 2, 2′, 2″,2″′, 2″″. By way of non-limiting example, the thickness of the radiationattenuating material may be from approximately 50 nm to approximately200 nm if a wavelength of from approximately 193 nm to approximately 248nm is to be used as the radiation.

In another embodiment of the imaging device 2′, 2″, the attenuationregion 10 includes at least one pixelated structure 14 formed from amaterial that is optically opaque to, absorptive (e.g.,non-transmissive) of, or partially transmissive of the wavelength orrange of wavelengths of radiation to which the imaging device 2′, 2″ isexposed, as shown in FIGS. 2A and 2B. The pixelated structure 14 may beformed of a plurality of so-called “dots” of the optically opaquematerial, which appear like a gray scale to the optics system used inthe photolithography process. The dots of the pixelated structure 14 maybe formed on a sub-resolution scale such that the size of the dots ofthe pixelated structure 14 may be smaller than the resolution of theoptics system used in the photolithography process. The assist features6, in combination with the pixelated structures 14, may control thetransmission of radiation in the attenuation region 10 of the imagingdevice 2′, 2″. By way of example, the optically opaque material may be ametal material, such as chromium (Cr), a chromium-containing compound,titanium nitride, tungsten, or combinations thereof. The assist features6 and pixelated structure 14 may be formed of the same material as theimaging features 8. In one embodiment, the assist features 6 andpixelated structure 14 are formed from chrome. The optically opaquematerial may be formed at a thickness of from approximately 400 Å toapproximately 800 Å. The optically opaque material may be formed on thesubstrate 4 by conventional techniques, such as by CVD or PVD, dependingon the material used. The assist features 6 and pixelated structure 14may be formed from the optically opaque material by patterning theoptically opaque material, such as by using conventional photomaskwriting techniques, which are not described in detail herein. By way ofexample, the optically opaque material may be patterned using an e-beamwriter or a laser-based exposure tool.

The assist features 6 in FIGS. 2A and 2B may be formed on pitch relativeto the imaging features 8 of the array pattern region 12. However, thepixelated structures 14 may be formed off pitch relative to the assistfeatures 6 and the imaging features 8. The patterned optically opaquematerial in the attenuation regions 10 may form the pixelated structures14 and assist features 6, as shown in FIGS. 2A and 2B. The pixelatedstructures 14 may be located between individual assist features 6,positioned proximate to the assist features 6, as shown in FIG. 2A, orin contact with the assist features 6, as shown in FIG. 2B. When theimaging devices 2′, 2″ are exposed to radiation, the pixelatedstructures 14 and the assist features 6 may prevent the radiation frompassing through the attenuation regions 10. The pitch of the pixelatedstructures 14 may cause the optics system to view the pixelatedstructures 14 as a uniform attenuating field. Due to the diffraction ofthe radiation by the assist features 6 and the pixelated structures 14,the radiation may fall outside the region to be captured by the lens ofthe optics system. The energy of the radiation is below a thresholdlevel (E₀), causing the optic system to view the pixelated structures 14as a uniform attenuating field. Consequently, the assist features 6 andpixelated structures 14 may not be formed (e.g., printed) on thesemiconductor device structure while the array features are formedthereon.

In other embodiments, imaging devices 2, 2′″ may be formed in which therelative sizes of the array pattern regions 12 and the attenuationregions 10 differ. By way of example, the array pattern regions 12 maybe larger in size than the attenuation regions 10, or the array patternregions 12 may be smaller in size than the attenuation regions 10, asshown by a comparison of these regions in FIGS. 1 and 3. In oneembodiment, the array pattern region 12, which corresponds to thepattern to be formed on the semiconductor device structure, may besmaller relative to the attenuation regions 10 of the imaging device 2,as shown in FIG. 1. Since the attenuation regions 10 are a large scalefeature, the attenuation regions 10 may provide attenuation of theradiation on a large scale. In addition, due to the relatively largearea of the attenuation regions 10, the method of the present disclosuremay be easier to implement than conventional OPC methods. In anotherembodiment, the array pattern regions 12 of the imaging device 2″′ maybe larger relative to the attenuation regions 10, as shown in FIG. 3.However, in both embodiments, the array pattern regions 12 and theattenuation regions 10 may include features (assist features 6 andimaging features 8) that are substantially on pitch. Therefore, incontrast to conventional assist features, which are smaller in size andare subject to aberration sensitivity, the attenuation regions 10 of theimaging devices 2, 2″′ of the present disclosure may have substantiallyreduced aberration sensitivity.

The imaging devices 2, 2′, 2″, 2″′ shown in FIGS. 1-3 may be used toform array features on the semiconductor device structure, such aspatterns of lines and spaces. In addition, imaging devices similar tothe imaging devices 2, 2′, 2″, 2″′ may be used to form differentpatterns on the semiconductor device structure. To form the patterns,which are described in more detail below, the imaging devices 2, 2′, 2″,2″′ may be positioned over the substrate 4 having a photoresist material(not shown) thereover. The photoresist material may be a conventionalmaterial used in a photolithography process and, therefore, is notdescribed in detail herein. As used herein, the term “substrate” meansand includes a conventional silicon substrate or other bulk substratehaving a layer of semiconductor material. As used herein, the term “bulksubstrate” includes not only silicon wafers, but alsosilicon-on-insulator (SOI) substrates, silicon-on-sapphire (SOS)substrates, epitaxial layers of silicon on a base semiconductorfoundation, and other semiconductor or optoelectronics materials, suchas silicon-germanium, germanium, gallium arsenide, or indium phosphide.The substrate 4 may, optionally, include other materials (not shown)thereon, such as materials from previous acts conducted during thefabrication of the semiconductor device structure. The substrate 4 andthe photoresist material may form an intermediate semiconductor devicestructure upon which the array features are to be formed. Forsimplicity, neither the photoresist material nor the underlyingmaterials, if present, are illustrated in the drawings.

The radiation of the desired wavelength or range of wavelengths may bedirected at the photoresist material of the intermediate semiconductordevice structure through each of the imaging devices 2, 2′, 2″, 2″′. Asthe radiation passes through each of the imaging devices 2, 2′, 2″, 2″′,the array pattern regions 12 and the attenuation regions 10 of theimaging devices 2, 2′, 2″, 2″′ may cause the radiation to be transmitteddifferently therethrough, enabling the pattern on each of the imagingdevices 2, 2′, 2″, 2″′ to be transferred to the photoresist materialoverlying the substrate 4. If the intensity of the radiation reachingthe photoresist material is greater than a threshold level (E₀), thephotoresist material may be cured by the radiation and subsequentlydeveloped and removed, producing a pattern in the photoresist materialthat corresponds to the pattern in the imaging devices 2, 2′, 2″, 2″′.While various embodiments herein describe the photoresist material as apositive-tone photoresist and the development thereof as a positive-tonedevelopment process, the photoresist material may also be anegative-tone photoresist that is developed using a positive-tonedevelopment process (e.g., TMAH), or a positive-tone photoresist that isdeveloped using a negative-tone development process (e.g., a solvent forunexposed regions). By way of example, the radiation may be transmittedthrough the array pattern regions 12 (the radiation passing therethroughis greater than E₀) and at least partially attenuated or substantiallyblocked by the attenuation regions 10 (the radiation passingtherethrough is less than E₀), depending on the material used to formthe assist features 6 or pixelated structures 14 in the attenuationregion 10. Following development, the patterned photoresist material maybe used as a mask to pattern underlying materials, such as the substrate4, producing the array features on a top surface of the substrate 4.

The imaging devices 2, 2′, 2″, 2″′ and methods of the present disclosuremay be used in a photolithography process to form the array features onthe substrate 4, where the array features are at a uniform pitch. Thearray features may be dense or isolated. By way of example, the arrayfeatures may be patterns of lines and spaces, such as a pattern ofconductive lines, such as access lines (i.e., wordlines), such as forflash memory. The imaging devices 2″″ and methods of the presentdisclosure may also be used to form two-dimensional patterns of interestso long as the array features to be formed are substantially on pitchand are of substantially the same size. Various examples of patterns tobe formed using the imaging devices 2, 2′, 2″, 2″′ and methods of thepresent disclosure are described in more detail below. For simplicity,each of FIGS. 4 and 8 illustrate a top surface of semiconductor devicestructures 16, 16′ that may be formed using the imaging devices 2, 2′,2″, 2″′.

FIG. 4 illustrates a semiconductor device structure 16 having a patternof lines 18 and spaces 20 that is formed utilizing the imaging device2″′ of FIG. 3. By way of example, this pattern may be used to produce aconductive line (i.e., access line, such as a word line) in a Not-and(NAND) flash memory device. As shown in FIG. 5, a simulation of anaerial image plot (the relative intensity of radiation utilized tocompletely remove the photoresist material overlying the substrate 4 asa function of position on the substrate 4) indicates that uniform lines18 may be formed (e.g., printed). The intensity threshold is a parameterof the photoresist material and defines the amount of radiation requiredto induce a sufficient change in the chemical properties of thephotoresist material so that the photoresist material may be fullydeveloped. As previously described, the photoresist material may be apositive-tone or a negative-tone and may be developed by a positive-tonedevelopment process or a negative-tone development process. Simulationtools for photolithography are known in the art, such as the PROLITH™system, which is commercially available from KLA-Tencor Corp. (Milpitas,Calif.). As evidenced by FIG. 5, the lines 18 may exhibit a good CDU andcontrast. In addition, the normalized image log slope (NILS) and CD maybe uniform (e.g., do not change) along the lines 18. Therefore, use ofthe imaging device 2″′ should enable simplified control of the CDU ofthe array features and no additional OPC may be needed. However, ifadditional correction is needed, the methods of the present disclosuremay be used in combination with conventional OPC methods. In contrast,in a conventional OPC method using an imaging device 22 as shown in FIG.6, which has features 24 of different size and that are not formed onpitch, the aerial image plot (FIG. 7) indicates that the lines are notuniformly formed and that the NILS and CD change along the lines.

FIG. 8 illustrates a semiconductor device structure 16′ having a patternof lines 18 and spaces 20 that is formed utilizing the imaging device 2of FIG. 1. This pattern may be used to produce a conductive line (e.g.,access line, such as a word line) in a NAND flash memory device. Asshown in FIG. 9, the aerial image plot indicates that uniform lines 18may be formed. In contrast, in a conventional OPC method using animaging device 22′ as shown in FIG. 10, which has features 24 ofdifferent size, the aerial image plot (FIG. 11) indicates that the linesare not uniformly formed.

The imaging devices 2′, 2″ of FIGS. 2A and 2B, which includes pixelatedstructures 14, may be used to form the pattern of lines 18 and spaces 20on the semiconductor device structure 16 shown in FIG. 4. As thedose-to-clear curve in FIG. 12 indicates, uniform lines may be formedwhen the imaging devices 2′, 2″ are utilized. Therefore, no additionalOPC may be needed.

Small isolated features, such as contacts, may also be formed on asemiconductor device structure utilizing imaging device 2″″, as shown inFIGS. 13 and 14. The imaging device 2″″ may include assist features 6 inthe attenuation region 10 and imaging features 8 in the array patternregion 12, with the assist features 6 separated from one another byradiation attenuating material 26. The imaging features 8 in the arraypattern region 12 may have a pattern corresponding to a pattern ofcontacts to be formed on the semiconductor device structure. The assistfeatures 6 in the attenuation region 10 and imaging features 8 in thearray pattern region 12 may be substantially the same size and formedsubstantially on pitch. The total area of the attenuation region 10 maybe significantly larger than the total area of the array pattern region12. Due to the substantially uniform pitch and size of the imagingfeatures 8 and assist features 6, the optics system may view the imagingdevice 2″″ as having a uniform field during photolithography. Althoughthe size and pitch of the assist features 6 in the attenuation region 10are substantially the same as the imaging features 8 in the arraypattern region 12, the assist features 6 are not formed by the opticssystems because the radiation attenuating material 26 attenuates thepassage of radiation therethrough.

In the embodiment illustrated in FIG. 13, a conventional positive-tonedevelop process may be used to form the isolated features. The assistfeatures 6 may be formed from a partially transmissive material, theimaging features 8 may be formed from an optically transparent material,such as quartz, the array pattern region 12 may be formed from apartially transmissive material, such as one of the materials previouslydescribed, and the radiation attenuating material 26 may be formed froman optically opaque material. Attenuation of the radiation may occur ina region of the imaging device 2″″ including the assist features 6. Inthe embodiment illustrated in FIG. 14, a conventional negative-tonedevelop process may be used to form the isolated features. The assistfeatures 6 and the imaging features 8 may be formed from an opticallyopaque material, the array pattern region 12 may be formed from anoptically transparent material, such as quartz, and the radiationattenuating material 26 may be formed from a partially transmissivematerial, such as one of the materials previously described.

The imaging devices 2, 2′, 2″, 2″′, 2″″ and methods of the presentdisclosure previously described may also be used to form semiconductordevice structures that include a plurality of dense array features (notshown) and a plurality of isolated array features (not shown). Thesemiconductor device structure may also include an iso-dense regionwhere the semiconductor device structure transitions from array featuresto assist features. During formation of such semiconductor devicestructures by conventional methods, the transition regions typicallyexhibit problems with CDU, CD bias, and CD asymmetry at edges of thearray. However, by utilizing the imaging devices 2, 2′, 2″, 2″′, 2″″ andmethods of the present disclosure, the problems with CDU, CD bias, andCD asymmetry may be reduced or eliminated.

By utilizing imaging devices 2, 2′, 2″, 2″′, 2″″ of the presentdisclosure in photolithography processes, a single attenuation act maybe conducted on a large region of the imaging devices 2, 2′, 2″, 2″′,2″″. Thus, the method of the present disclosure may be easier toimplement than conventional OPC methods. The imaging devices 2, 2′, 2″,2″′, 2″″ may also be utilized in conventional photolithography processeswith few modifications to existing equipment and hardware. Inconventional OPC methods, radiation may fall outside of the lens of theoptics system, which results in high aberration sensitivity. However,with the imaging devices 2, 2′, 2″, 2″′, 2″″ and methods of the presentdisclosure, substantially all of the radiation falls within the lens,giving robust aberration performance. Since the assist features 6 areformed at substantially the same feature size and pitch as the imagingfeatures 8, the optics system used in the method of the presentdisclosure may easily image the assist features 6, enabling lowaberration sensitivity. Furthermore, since the assist features 6 areformed in a periodic manner across the attenuation region 10, the assistfeatures 6 may be optically viewed as a uniform field by the opticssystem. Thus, the assist features 6 of the attenuation regions 10 mayparticipate in imaging even though corresponding features are not formedon the semiconductor device structures 16, 16′. In contrast, inconventional OPC methods, the optics system does not optically recognizethe assist features because these assist features are formed at asub-resolution scale. In the imaging devices 2, 2′, 2″, 2″′, 2″″ andmethods of the present disclosure, the attenuation regions 10 may beviewed optically as gray scale, in contrast to the array pattern regions12.

CONCLUSION

An embodiment of the present disclosure includes an imaging device. Theimaging device comprises at least one array pattern region and at leastone attenuation region. A plurality of imaging features in the at leastone array pattern region and a plurality of assist features in the atleast one attenuation region are substantially the same size as oneanother and are formed substantially on pitch.

Another embodiment of the present disclosure includes a method offorming an imaging device. The method comprises forming a plurality ofimaging features and a plurality of assist features on a substrate. Theplurality of imaging features and the plurality of assist features aresubstantially the same size as one another and have a substantiallyuniform pitch.

Yet another embodiment of the present disclosure includes a method offorming a semiconductor device structure that comprises exposing aphotoresist material to radiation through an imaging device. The imagingdevice comprises at least one array pattern region and at least oneattenuation region. Features in the at least one array pattern aresubstantially the same size and formed substantially on the same pitchas features in the at least one attenuation region. Portions of thephotoresist material are removed to form a pattern in the photoresistmaterial. The pattern is then transferred to the structure.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, the invention is not intended to be limited to the particularforms disclosed. Rather, the invention is to cover all modifications,equivalents, and alternatives falling within the scope of the inventionas defined by the following appended claims and their legal equivalents.

What is claimed is:
 1. An imaging device, comprising: a first regioncomprising imaging features and a second region comprising assistfeatures, the second region configured to inhibit formation of featureson a portion of a structure corresponding to the second region; whereinthe imaging features and the assist features are substantially the samesize as one another and are substantially on the same pitch.
 2. Theimaging device of claim 1, wherein the first region is configured toform at least one of access lines and contacts on a portion of thestructure corresponding to the first region.
 3. The imaging device ofclaim 1, wherein the imaging features are formed of at least one ofmolybdenum silicon, molybdenum-doped silicon oxide, molybdenum-dopedsilicon oxynitride, molybdenum-doped silicon nitride, molybdenumsilicide, chromium oxide, and tantalum silicon oxynitride.
 4. Theimaging device of claim 1, wherein the assist features are formed of atleast one of molybdenum silicon, molybdenum-doped silicon oxide,molybdenum-doped silicon oxynitride, molybdenum-doped silicon nitride,molybdenum silicide, chromium oxide, and tantalum silicon oxynitride. 5.The imaging device of claim 1, wherein the imaging features are 180° outof phase with open areas on the imaging device and the assist features.6. The imaging device of claim 1, wherein the first region comprises anoptically transparent material.
 7. The imaging device of claim 6,wherein the optically transparent material comprises quartz.
 8. Theimaging device of claim 1, wherein the assist features have a thicknessof from approximately 50 nm to approximately 200 nm.
 9. A method offorming an imaging device, comprising: forming a first region comprisingimaging features and a second region comprising assist features on asubstrate, the second region configured to inhibit formation of featureson a portion of a structure corresponding to the second region; whereinthe imaging features and the assist features are formed to be ofsubstantially the same size as one another and substantially on the samepitch.
 10. The method of claim 9, wherein forming a first pattern regioncomprising imaging features and a second region comprising assistfeatures on a substrate comprises forming the imaging features from anoptically opaque material.
 11. The method of claim 10, wherein formingthe imaging features from an optically opaque material comprises formingthe imaging features from at least one of chromium, achromium-containing compound, titanium nitride, and tungsten.
 12. Themethod of claim 10, wherein forming the imaging features from anoptically opaque material comprises forming the optically opaquematerial at a thickness of from approximately 400 Å to approximately 800Å.
 13. The method of claim 10, further comprising patterning theoptically opaque material.
 14. The method of claim 13, whereinpatterning the optically opaque material comprises using an e-beamwriter or a laser-based exposure tool.
 15. The method of claim 9,further comprising forming pixilated structures on the substrate offpitch relative to the imaging features and the assist features.
 16. Amethod of forming a semiconductor device structure, comprising: exposinga photoresist material to radiation through an imaging device, theimaging device comprising: a first region and a second region, thesecond region configured to inhibit formation of features on a portionof a structure corresponding to the second region, wherein imagingfeatures in the first region are substantially the same size andsubstantially on the same pitch as assist features in the second region;removing portions of the photoresist material to form a pattern in thephotoresist material; and transferring the pattern in the photoresistmaterial to the structure.
 17. The method of claim 16, wherein removingportions of the photoresist material to form a pattern in thephotoresist material comprises removing portions of the photoresistmaterial to form a pattern of lines and spaces.
 18. The method of claim16, wherein transferring the pattern in the photoresist material to thestructure comprises forming a pattern of conductive lines.
 19. Themethod of claim 16, wherein transferring the pattern in the photoresistmaterial to the structure comprises forming a pattern of contacts. 20.The method of claim 16, wherein exposing a photoresist material toradiation through an imaging device comprises exposing the photoresistmaterial to radiation having a wavelength of from approximately 193 nmto approximately 248 nm.